Unit 18

In a purely inductive circuit, the CEMF waveform is _____ out-of-phase with the applied voltage waveform.

180 Degrees

The waveform of the CEMF is _____ out-of-phase with the applied voltage.

180 Degrees

In an inductive circuit, the CEMF waveform is 90 ° out-of-phase with the current waveform and 180 ° out-of-phase with the applied voltage waveform by, making the voltage waveform lead the current waveform by _____.

90 Degrees

Self-induced voltage is 180 ° out-of-phase with the _____. When the applied voltage is at its maximum in one direction, the induced voltage is at its maximum in the opposite direction.

Applied Voltage

The induced voltage in a conductor carrying alternating current opposes the change in current flowing through the conductor. The induced voltage that opposes the current flow is called "_____."

Counter-electromotive force, CEMF or Back-EMF

For ac circuits, the ac _____ of a conductor must be taken into consideration.

Eddy currents, skin effect, and resistance

True or False: Eddy currents are small independent currents induced within the conductor because of direct current.

False

True or False: Conductor resistance is directly proportional to the conductor's length and cross-sectional area.

False. Directly proportional to length and inversely proportional to cross-sectional area

A common practical use of induction is for _____.

Generators, transformers and motors

The movement of electrons caused by an external magnetic field is called "_____ current," and the associated potential that is established is called "_____ voltage."

Induced

The direction of the overall magnetic field around the conductor follows the _____ rule, based on the Electron Current Flow Theory.

Left-hand

In order to induce voltage, relative motion is required between a conductor and a _____ field. This is the basis of the generator and transformer.

Magnetic

In dc circuits, the only property that affects current and voltage flow is _____.

Resistance

As the alternating current through a conductor increases, an expanding and collapsing electromagnetic field through the conductor induces a voltage within the conductor. This is known as "_____ voltage."

Self-induced

True or False: Because an iron core provides an easy path for magnetic flux, windings with soft iron cores produce a greater self-inductance than windings with air cores.

True

True or False: The magnitude of self-induced voltage within a winding is directly proportional to the current flow, the winding, and the frequency at which magnetic fields cut through the winding.

True

True or False: When alternating current increases, the polarity of the CEMF within the conductor tries to prevent the current from increasing.

True

True or False: When electrons move, the magnetic fields of the individual electrons combine to produce an overall magnetic field. The greater the current flow, the greater the overall magnetic field around the conductor.

True

True or False: When the alternating current decreases, the polarity of the induced voltage within the conductor tries to prevent the current from decreasing.

True

Self-induced voltage opposes the change in current flowing in the conductor. This is called "inductive reactance" and it is abbreviated _____.

Xl

The expanding and collapsing magnetic field within the conductor induces a voltage in the conductors (CEMF) that repels the flowing electrons toward the surface of the conductor. This is called "_____."

skin effect